Hello Heiko,
OK with me, but I think I'd rather turn it around:
Fog means water droplets or minute ice crystals close to the surface
which reduce visibility in air to less than 1000m.
"X_area_fraction" means the fraction of horizontal area occupied by
X.
This is because I think of fog as 'a type of cloud' rather than 'an
amount of visibility'.
What do you think?
All the best,
David
---- Original message from Heiko Klein (09AM 07 Aug 13)
> Date: Wed, 7 Aug 2013 09:22:22 +0200
> From: Heiko Klein <Heiko.Klein at met.no>
> User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130623
> Thunderbird/17.0.7
> To: David Hassell <d.c.hassell at reading.ac.uk>
> CC: Jonathan Gregory <j.m.gregory at reading.ac.uk>, cf-metadata at cgd.ucar.edu
> Subject: Re: [CF-metadata] Standard name for fog as area fraction
>
> Hello David,
>
> I think we agree on the important parts about fog:
>
> * visibility in air < 1000m
> * caused by water (i.e. not by dust, which would be haze)
> * near-surface (~ human eyes height)
>
> Coming to the exact wording is more difficult. The term 'cloud'
> might include dust (Saharan dust clouds) and exclude radiation fog,
> so I wouldn't like to use it. 'humidity' is invisible as you note,
> so I will drop that. water droplets might exclude ice-fog. What
> about:
>
>
> fog means visibility in air < 1000m due to water
> droplets or minute ice crystals close to the surface.
> "X_area_fraction" means the fraction of horizontal area occupied by X.
>
--
David Hassell
National Centre for Atmospheric Science (NCAS)
Department of Meteorology, University of Reading,
Earley Gate, PO Box 243,
Reading RG6 6BB, U.K.
Tel : +44 118 3785613
E-mail: d.c.hassell at reading.ac.uk
Received on Fri Aug 09 2013 - 08:48:43 BST
